Clutch



H. A. KNOX Aug. 13, 1946.,

CLUTCH Filed MarchB, 41944 2 Sheets-Sheet 1 Aug. 13, 1946.. H. A. KNOX@2,405,582

I CLUTCH Filed March s, 1944 V 2 sheets-sheet 2 Figa- Patented Aug.13,1946

UNITED STATES PATENT OFFICE CLUTCH Harry A. Knox, Washington, D. C.Application March 8, 1944, Serial No. 525,511

17 Claims. l (Cl. 192-68) (Granted under the act of March V3, 1883, asVamended April 30, 1928; 370 O. G. 757) The invention described hereinmay be manufactured and used by or for the Goverment for governmentalpurposes without the payment to me of any royalty thereon.

The invention relates to power transmission clutches, and has for anobject to effect improvement in a disc clutch operated through anaxially slidable throwout member.

The invention aims specially to improve connections between a slidingsleeve and a presser plate on a rotative member whereby frictionelements of respective rotating members may be cl-amped together to formthe clutch connection.

A further important purpose is to offer an improved construction foroperating the presser plate to attain high clutching eii'iciency withina moderate space.

It is a specially important object of the invention to present novelmeans for amplifying the force applied through a spring element whileinvolving only a moderate extent of movement of the spring element.

It is well appreciated that one of the most important objects inclutches for power transmissions between internal combustion motors andfinal drive in motor vehicles is economy of space, especiallylongitudinally of the axis of rotation of the driving and drivenmembers, or longitudinally of the axes of the gearing of speed-changingtransmission; and ordinarily all of the axes indicated are laid in thesame direction, making the reduction of space required for the clutchstill more important.

CIS

In the production of military material there are several factors makingthis attainment paramount. First, all possible space is desired withinthe length of the Vehicle for many auxiliaries, second, the running gearis in many cases shortcoupled, and to this is often added a four-wheeldrive making further requirement for such economy of space.

Recently the use of radial airplane-type motors, especially in tanks,has put a further premium on space, because of the size of these motors,and in tanks, the limitations imposed by the use of armor (making itnecessary to encompass as small a space therewith as possible and yetprotect the power plant, driver and large crew) and the multiplicationof gun units radio equipment and other elements have put a barrier inthe way of amplifying conventional clutch designs to carry theprodigious loads involved by the great mass of these vehicles and thegreatly enlarged power output required to move them at the high speedsdemanded in the current war. The enlargement of springs in usuallocations to alord the necessary clutch pressure, and the multiplicationof discs and clutch surfaces have reached boundaries of pract-icability,without a satisfactory solution of the problem. The use of more than onedisc is objectionable because of the greater longitudinal space requiredand also the added machine cperations, fitting and assembly operations,and added materials. Sliding and keying or splining of the multiplediscs on both driving and driven members is a serious objection. Thegreater pressures required where a single disc is employed of moderatediameter has been an insurmountable difficulty, where the limitations ofspace, economy in material and reasonable ease of assembly aresatisfied; and it is one of the most important motives in this inventionto enable the production of a single disc clutch and an amply adequatepressure applying means to clamp the disc to relatively rotating partsso as to transmit the high torque involved in tank power plants, and atthe same time gain marked advantages and improvement in compactness,eiciency, economy of manufacture and ease of operation and repair.

It is a special aim of the invention to provide for a liberal clearanceof opposed clutch faces at the same time that a high pressure springaction is provided for, enabling operation of the device by a foot pedalwith moderate effort, yet using a small and compact readily assembledspring device.

A specific end in view is to present a novel assembly of clutchoperating connection of high leverage value so constructed and arrangedas to be affected in a minimum degree by centrifugal force.

Another important attainment is the presentation of a' constructionhaving the foregoing advantages, yet which is adapted to be producedwith a minimum of difficulty in manufacture, and assembled manually withfew fastening devices, and a minimum requirement for the use of tools. v

It is a further object to aord a novel toggle construction and operatingmeans therefor enabling the application of the high pressures to theclutch which may be expected from the use of such a device 'in a simpleand rugged construction yet one light in weight compared to theproportions of conventional clutch construction and the high degree offorce transmitted.

A further important attainment in view is to enable ready access to allparts of the clutch operating connections for replacement or repair witha good working space therearound for manipulation of convenient tools.

It is also sought to oier a construction which will have great value forproduction in smaller sizes, for incorporation in small passenger carsand trucks.

Additional objects, advantages and features of invention reside in theconstruction, arrangement and combination of parts involved inH theembodiment of the invention, as will appear or be understood from thefollowing description and accompanying drawings, wherein:

Fig. 1 is a section elevation of the rear side of a clutch constructedin accordance with my in Vention;

Fig. 2 is a vertical section on the line 2--2 of Fig. 1;

Fig. 3 is a fragmentary section on the line 3-3 of Fig. l;

Fig". 4 is a` fragmentary section on the line #-4, of Fig. 1;

rlhe Figures 1 and 2V are drawn approximately onefhalf of the full sizeof apparatusheretofore constructed.. for tank Se Reierring. to thedrawings, there is shown. the, rear, extremity of. a motor shaft lil, orprime mover, haying a tapered. conical portion ll a distance forwardly,ending rearwardly ata cylinf. drical part l2 which extends over asubstantial distance rearwardly from the part ll, a splined part I3.,and. a. relieved tenori t4 is formed on the extremity of the shaft, theouter or rear part which isexternally threaded to. receive a forcingmit. llito be referredto.

A. Dlanform circular clutch base plate i5 is provided, constituting thedriving member of the clutch and having a hubY I6 bored and splined tofitthe splined cylindrical part 1.3, of the shaft, with a forward flarel fitting the tapered. part I l. 0f the shaft. The hub. stops short ofthe threaded part of the, tenori and; is. conically relieved interiorlyto receive a wedgecollar I1 slide able on the forward smooth. part ofthe tenori and fitted to the conical end of the bore in the hub. It ispressed forward by a forcing nut i8 screwed onthe extremity of thetenon, whereby the hub is. likewise forced. on tothe conical. part ilvofthe shaft lil, witha greater extent of sup-. port longitudinally. thanafforded by thering.

I henut .Ik is formed with.I an` externalA hardcylindrical face. to..serve as a rear bearingfor the driven member as will be described.Theinut has a. swivel connection with. the collar sothat unscrewing ofthenut willdraw out the collar.

The base plate is ofsubstantial mass so that itmay serve as a flywheel,and includes-a` peripheral cylindrical rearward extension or flangeA i9concentric with the shaft. It has at its rear'edge a series of fourequally spaced lugs 2B- projected inwardly toward the shaft parallel tothe plate A drivenv member 2l is revolubl'e onY the hub and nut,consisting of a circulardisc 2-2 of a radius less than that of theinneredges of the lugs 2.0 so that it'may be moved axially into and out ofoperative position. The disc has opposite facings 23 of suitablefriction material.

The disc body is planiform over an outer annular zone 24 and throughouton its forward surface, but is progressively thickened from the zone 24inwardly in a rearward direction. Y

The disc has an integral rearwardly extended hub 25, its interior borebeingrelieved at the forward end-to accommodate roller bearings 28coupling hub, a grease injection hole 29 being provided therethrough forconventional grease or oil supply fittings. Immediately adjacent the endY or the hub l a radial port 30 is formed through the hub 2E for passageof lubricant from within the hub to a throwout sleeve felt to bedescribed.

A concentric annular recess 3l is formed in the forward face of the discnear its axial bore, the inner side thereof having an overhang 32 tothrow off lubricant escaping from the bearing 26 and the base plate I5has an inwardly inclined annular rib. 33 extended rearwardly intotherecess 31, forming a gutter 34 to receive lubricant thrown oli by theoverhang 32, drain holes 3.5. leading from the bottom ofv the. gutterforward through the plate l5 and inclined away fromy the shaft, so. asto discharge oil forwardly from; the gutter.

A presser plate 35 is mounted rearwardly of the disc for translativeaxial movement toward and away from the disc and base plate. Thispresser plate consists of a thick planiform annular body coextensivewith the zone 24 of the disc and having a medial concentric stiffeningrib 3 1, and four radial support lugs 3B. spaced to aline with the lugs26 respectively. The lugs 2l! and 38 each includes an angle of about 30degrees, so as t0` each receive therethrough three heavy assembly andpresser plate centering bolts 3,9 securing brackets lil vto the rearfacesof the lugs 2n. The brackets project inwardly behind the presserplate and are also inclined longitudinally rearward. At their inner and.rearward parts they2 are formed with integral radially bored and splitpin holding clamp collars 4i, in which are inserted enlarged.cylindrical pin bodies l2v exposed at the outer sides of the collars andslotted for. rotation by a screw driver or other tool at times, as-willbe explained thev collars are splitat` theirv outersides in a planeparallel' to that oftheplate l5, andthe outer rearward spring arm Lilthus formed is extended and` apertured as usual in such clamps, toreceive therethrough a clamp bolt 44, screwed into a correspondingthreaded hole in the body ofA the bracket under the arm.

The pin body 42 has aneccentric pivot stud 45- extended longitudinallythereof and inward onv arad-ial axis, to receive one memberof a toggleforwardlybeyond the lug 20 and engaged snuglyV andslidably through holesin the lugs 38 of the presser plateV so as to support thelatter'slidably.

On the rear side of the presser plate there are quadriradiate raisedbearings Sii, extending partly across t-he rear face of the presserplate and` inwardly thereof a distance, the plate having correspondinginward strengthening extensions 4 1 thereunder, these stop outwardly ofthe hub 25 a substantial'distance. The bearings consist substantially ofrib portions radially'bored to form a semicylindrical bearing surface48; a slot' 49'being formed through one side throughout the length ofthe bore. One side 5I of the slot 49 in a clockwise direction is tangentto the bearing face 48 and in a plane parallel to the axis of the hubwhile the opposite side 52 of the slot is parallel to the side 5l andlocated approximately 215 degrees from the radius of the tangentmentioned, so that the clearance in the mouth of the slot iscorrespondingly and substantially less than the diametrical measurementof the bore.

A crank shaft 53 is provided fitted revolubly in the bearing andextending beyond each end thereof. This shaft is formed with a flat 54throughout its length parallel to the axis of the shaft and subtendingan angle of approximately 90 degrees more or lless on the cylindricalsurface of the shaft. As a result the measurement on a line normal tothe face 54 through the axis of the shaft to its periphery is less thanthe width of the slot and when the shaft is presented at the slotparallel to the bearing and with the at adjacent the side 52 the shaftmay be moved laterally through the slot to a `bearing in the bore. Whenthen rotated to its approximate operative position as in Fig. 3, withthe flat 55 extended across the slot, the shaft is retained firmly inplace. The principal loads communicated tothe shaft are sustained by theinner part of the bearing and near the side 52 of the slot. The shaft isformed with two integral upper and lower arms or levers 55-55 of shortradius, each on the same radial' plane of thev shaft, extendingobliquely across the plane of the flat 54. The upper arm 55 is formedwith an enlarged base 51, providing a shoulder 58 resting against theinner end of the bearing 50.

The upper crank arm is provided with a wrist pin 59 fixed thereon andextended upwardly on an axis parallel to the projected axis of the shaft53, while the lower arm 55 is provided with a similar pin 6D, alsoextended upward, that is, toward the clutch axis.

' A compression toggle lever link 6I is fitted on the stud 45 (retainedby washer and cotter Eil) and wrist pin E5, and the aggregate of theradii of the arm 55 and link 6l is greater than the distance between theaxes of the shaft 53 and stud 45.. This last named distance is variableby rotating the pin body 42, .when the clamp 4l is `released, throwingthe stud 45 toward or from thepresser plate. It is apparent that the arm5`5'and link 6I are capable of functioning as toggle levers by movementtoward their dead center relation.

On the hub 25 there is slidable a throwout sleeve 62 at the rear end ofwhich a channel B3 is formed exteriorly, in which a throwout ring 54 isrevoluble, operated conventionally by a usual yoke not shown toreciprocate the sleeve as desired. At its forward end four thrust arms65 are formed or mounted on the sleeve extending nearly tangent to thesleeve in a counterclockwise Edirection and formed with respectiveknuckles 55 in which there are xed respective pivot bolt studs 'il onaxes parallel to the respective shafts 53 .nextY to the bases of thearms 65. A thrust link connection is formed between the studs 6'! andrespective adjacent wrist pins 59, so proportioned vthat at the forwardposition of the sleeve 62, the

wrist pin and stud may lie in the same plane normal to the axis of thesleeve-in other words, in dead center relation. The linkage in thepresent instance consists of a rod 68 having a'transversely bored headB9 receiving the wrist pin 59 sliidably'and revolubly therethrough andremovabler inwardly freely when the shaft is away from its bearing. AU-shaped yoke 10 has its arms 1| apertured and engaged revolubly on thestud 61. The head l2 of this yoke is apertured to fit slidably aroundthe rod, and the latter has a threaded tenon at its extremity betweenthe arms of the yoke, on which a square nut 'I3 is screwed, tted snuglybetween the arms 'H by which it is held against rotation on the rodafter assembly. The nut constitutes a limiting means to the rearwardmovement of the yoke head 1I on the rod, and may be adjusted if desiredby unscrewing and removing the stud 6T then rotating the yoke and nuttogether in the proper direction.

The head 69 affords a shoulder 'M around the rod next the wrist 59, andbetween this shoulder and the head of the yoke 10 a multiplicity ofBelleville spring washers 'l5 are confined, slidably engaged on the rodand arranged in pairs with their concave faces opposed. These washersare in such number that when the throwout sleeve is at its rear limitthe washers are moderately confined, and when the sleeve is forward todead center relation as in Fig. l the washers are compressed to adesired maximum. The full extent of this movement need not be more thanoneeighth inch in a heavy duty clutch, although this may be increased bydecreasing the number of washers and properly proportioning the latterto give the desired maximum pressureforce .under the extent ofcompression involved when the linkage is in dead center position.

With the linkage between the throwout sleeveand crank shaft in deadcenter position and the presser plate 3S fully engaged against the discand facing, the member 42 is preferably so adusted initially that thelink lever SI and crank lever 55 are. short of dead center position tothe extent of between live and ten degrees of angular movement on theiraxes. a considerable further operation of the toggle linkage when thefacings become somewhat worn, by expansion or extension of the linkagethrough action of the Belleville washers, which, while the parts remainin dead center relation will nevertheless effect a further thrust uponthe inner crank arm 55, so as to operate thetoggle through a furthermovement than initially set for. Also, at dead center position of thelinkage to the sleeve, and initial adjustment of the togglel device, thecrank arm 55 is somewhat inclined at its outer part toward the axis ofthe sleeve.

In order to support the sliding junction of the yoke 10 and rod E8, thenuts 'i3 are each provided with longitudinally extended rest arms 16 atopposite sides, adjacent and against respective arms 'il of the yoke.These arms are as wide as the arms of the yoke and have longitudinalguide slots 'H open through their outer ends and receiving the bodyportion of the stud 6'! therein for rotationwhen the stud is screwed orunscrewed, but, more important for sliding movement of the stud in theslots as the yoke 'lf3 compresses the washers 'I5 or withdrawsoppositely on the rod 68. When the washers expand the outer end of therod is thus supported slidingly on the stud independently of the yokelil, preventing binding or excessive wear of the latter against the rod.

In the use of this construction, the toggle device will be consideredbroadly as including connecting portions 45-56-55--6L the linkage 61 to15, the shaft 53, and the crank 55. The'mechanism being assembled asdescribed, the released position of the parts will be substantially asindi- 'Ihis allows for:

cated in dotted lines in Fig. 4. The Belleville washer unit or linkagewill be fully extended so that. the head 12 of the yoke 1G wil bepressed against the nut 13, and the stud 61 will be at the rear limit ofits movement, in full size about one and three quarter inches from deadcenter position. The inner crank arm 55 will be inclined inwardly towardthe axis ofthe sleeve to a maximum and the toggle device portionl5-55-60- Bi will be broken from dead center position further than shownin Fig. 3 to the extent. involved by the dotted position of the innercrank arm 55 in relation to its full line position in Fig. 4. Thisposition of the toggle will have resulted in drawing the shaft 53rearwardly and with it the presser plate 36, slidingly on the stud ends46 of the bolts 39, and freeing the disc 22.

On operation of the pedal or other levers customarily employed tooperate the sleeve, the latter is moved slidingly forward, applyingpressure throughout the linkage 81 to 15 to the crank arms 55 so as tomove these outward and swinging the toggle device portion 56-6-6i towarddead center position. In the early part of this operation, relativelysmall opposition to compression will be manifest and the movement willrequire only moderate force despite the low advantage in the leverageinvolved. As the resistance of the washers increases so does theadvantage in leverage, so that moderate effort will still effect themovement required under increasing pressure applied at the clutch faces.The operation of the clutch pedal as last described may be by springaction or manual, and may include means `to limit forward. movement 1 ofthe throwout sleeve, as in my Patent Number 2,380,971, issued August .7,1945.

Among the advantages of my invention in addition to those firstmentioned, are the small number of fastenings such as pins and nuts orscrew threaded or other fastenings of or between operative partsrequiring tools or tooling in assembly, or disassembly of the mechanism.Thus, centrifugal force will hold the link lever 6| in operativeposition so that only a small cotter pin BI is sufficient, required onlyduring assembly and when the parts are at rest. Likewise the connectionof the linkage with the wrist 59 requires no fastening at all, theclearance between the wrist and sleeve being insuflicient for detachmentof the head 59, and the latter being thrust home on the wrist bycentrifugal force during operation. The assembly and disassembly o-f theextensiblelinkage also may be effected manually without a fixedfastening, the nut 'i3 being unscreWab-le Lby rotating the yoke 'lilafter dismounting, The shaft 53 is removable without Vtools afterdismounting the linkage from the stud Bl, by extracting the Cotter pin6i', litfing off the link 6I, and after rotating the shaft clockwise asviewed in Fig. 3 to `bring the flat 5G parallel to the tangent side 5|of the bearing slot beside the shaft. At this last named position of theshaft the linkage may be lifted from the inner wrist 59, manually. Thelinkage may be disassembled and assembled manually, since the range ofmovement of the nut i5 on the threaded tenoned end of the rod issufficient to relieve the discs of compression in outward direction andto effect full compression of the discs when screwed inward to theoperative position of the nut previously described. The wall of thebearing 50 is exteriorly relieved (as shown in Figure 3') at one side atitsouter end, adjacent the side 52 of the bearing slot, in line with thepath of the outer wrist B0, so as to permit the latterto be swung'toposition for clearing the shaft from the bearing.

While I have disclosed this invention with particularity in its bestconstruction knownl to me, it will nevertheless be understood that this.is

purely exemplary, and that changes in construction, arrangement andcombination of parts, substitution of materials, and equivalentsmechanical and otherwise, may be made therein Without departing from thespirit of the invention as set forth in the appended claims, wherein Iclaim:

l. in a clutch of the character described, a rotary driving member and acoaxial rotary driven member on a main axis axially movable toward andaway from the driving member, an axially movable presser plate xedangularly with the driving member, a toggle device having one memberelement based on the presser plate and the other on the driving memberon toggle axes substantially radial to the main axis, one mem- :berelement thereof having an operating rocker shaft extended inwardly to anare of' rotation on` said main axis lof less radius than that of thetoggle and having a crank at its inner part, a slide axially movable onand angularly fixed with the driving member, and a linkage connectedbetween the slide and crank at an angle to the latter and at an angle tothe path of relative axial movement of its connection with the slide,and means to operate the slide,

A2. The structure of claim 1 in which said linkage is constructed andmounted on said slide for movement relatively thereto in a planeparallel to the said main axis.

3. The structure of claim 1 in which said linkage is constructed andconnected to said slide at a, distance radially outward from said mainaxis adjacent the radius of the arc of rotation of the crank around themain axis and spaced angularly from the crank in relation to said mainaxis a distance equal to the length of the linkage, whereby a deadcenter leverage may be applied with a minimum of elements o-fcentrifugal force included.

i. The structure of claim 1 in which said shaftv is radial, and theplane of operation of the toggle is tangent to the path of translativemotion of the toggle around the said main axis.V

5. The structure of claim 1 in which said shaft is radial, said togglehaving its outer pivots on axes radial to said main axis, means toadjust the spacing of said pivots, said crank being movable with saidshaft over a path having its mean adjacent a radialplane of said mainaxis and said linkage is of aV length to lie on dead center between itsconnection with the sleeve and the crank.

6. The structure of claim 1 in which a bearing for said shaft is formedon said presser member at its rearv side, the said bearing having alongitudinal slot whose diameter is of a width less than the diameter ofsaid bearing opening therefrom toward the rear,V one side of said slotbeing tangent to the said bearing, the said shaft having a at disposednormally across the said slot, the transverse dimension of the shaft ona line through its axis normal' to the said flat being less that thewidth of the slot.

7. The structure of claim l in which the presser plate has a bearing forsaid shaft extending generally radially, said shaft being revolubletherein and having a shoulder at its inner part against the bearing totransmit thereto centrifugal force evolved on rotation ofthe shafttranslatively aroundv said main axis, a wristv pin' mounted in saidcrank and extending toward said main axis, said linkage including aterminal member set slidably and revolubly on the wrist pin and havingan applied position extending at a tangent 'to the path of said wristaround said main axis, said slide having an offset bearing for the outerend of the linkage.

8. A linkage for the uses described consisting of a pressuretransmitting member, a pressure applying member having angular limitedconvergent movement in relation thereto a link rod pivoted on thetransmitting member, a pivot yoke on the pressure applying member andslidable on the rod, a nut having threaded engagement with the extremityof the rod outwardly of the yoke to limit outward movement of the yokeon the rod, and a multiplicityof Belleville washers carried by said rodbetween said yoke and said transmitting member and adapted to transmitthe pressure applied by Said pressure applying member from said yoke tosaid transmitting member.

9. The structure of claim 8 in which said yoke has parts extending inclose iitting engagement with said nut and beyond, and the whole beingproportioned so that at the pressure applying limit of movement of thepressure applying member said yoke will be clear of the nut.

l0. In a clutch a rotating driving plate, a concentric rotatable drivenmember of less diameter, an axially movable presser plate rearwardly ofthe driven member, the driving plate having outer rearwardly extendedparts and inwardly extended ears thereon, said presser plate havingcorresponding ears adapted to pass inwardly between the rst named earsunder relative axial translative movement of the presser plate and tolie in registry with the rst named ears within said rearwardly extendedparts, brackets mounted adjacent the first named ears, pressuretransmitting means mounted upon said brackets and engageable with thepresser plate, and headed bolt members having threaded engagement in therst named ears and slidable in the brackets and through the second namedears in supporting engagement therewith and having their heads inclamping engagement against said brackets.

11. In a clutch, a rotating driving plate, a concentric rotatable drivenmember of less diameter, an axially movable concentric presser plate xedangularly with the driving plate rearwardly of the driven memberconstructed to clamp the driven member against the driving plate. saiddriving plate having rearwardly extended parts, inwardly extendedbrackets thereon spaced rearwardly of the presser plate, radial bearingsadjacent said brackets, a shaft revoluble in each said bearing having arearwardly extended toggle arm, a toggle link pivoted on the adjacentbracket and pivoted to the toggle arm, a crank on the shaft inwardly ofthe toggle extended in the same general direction as said toggle arm, alink extended therefrom having an operated position transverse to aradial plane of said driving plate, a coaxial slide axially movable onthe axis of the driving plate and a thrust arm for each last named linkon the slide pivotally connected to the link and movable rearwardly withthe connected end of the link from said operated position, and means tooperate the slide.

l2. The structure of claim 11 in which means is ,included to adjust thepivot of said toggle link on the bracket toward and away from thedriving plate, and in which said last named link is extensible, andelastic expansive means coacting between the end portion of the link tomaintain a predetermined transmission of pressure between the slide andsaid crank.

13. The construction in claim i2 wherein the last named link includes arod having a head revolubly mounted on the crank, a U-shaped yoke havingan apertured head slidable on the rod, a stud on the respective thrustarm engaged through the arms of the yoke the rod having a threadedextremity' extended between said arms of the yoke a nut screwed on therod and held between the arms, and aprotractile spring device engagedloosely around the rod and conned between the heads or the rod and yoke.

14. A clutch comprising clutch members relatively revoluble on a mainaxis, a toggle device, an element of which is mounted on one clutchmember, and having pushing connection with the other and having itsmembers pivoted on axes approximately radial with respect tc said mainaxis, an eccentric linked to the toggle for adjustment of the same, athrowout member slidable relative to and fixed angularly relative to thetoggle on said main axis, a pivot member on and xed axially with thethrowo-ut member closely adjacent a tangent of the arc of movement ofthe toggle device around said main axis and an elastic extensible shaftconnected between the said eccentric and said pivot member on thethrowout and having a minimum length equal to the distance between theeccentric and pivot member when the throwout member is in position withthe eccentric and pivot member in a plane normal to said main axis,constituting a dead center relation.

l5. The structure of claim 8 in which said yoke has parts extendedbeside said nut and beyond, the whole being proportioned so that at thepressure applying limit of movement of the pressure applying member saidyoke will be off bearing at the nut, said nut having a longitudinalextension slidingly engaged with the pressure applying member forsupport of the rod end.

16. The structure of claim 1 in which an operating crank is formed onsaid rocker shaft, said linkage being pivoted on said slide and the endof said crank, said pivot on the slide being angularly spaced from theaxis of the rocker shaft around the axis of the clutch and said linkagebeing of a length to permit movement of the slide to position bothpivots of said linkage in a common plane normal to the main axis.

17. The structure of claim l in which an operating crank is formed onsaid rocker shaft, said linkage being pivoted on said slide and the endof said crank, said pivot on the slide being angularly spaced from theaxis of the rocker shaft around the axis of the clutch and said linkagebeing of a length to permit movement of the slide to position bothpivots of said linkage in a common plane normal to the main axis, saidlinkage being movable to and beyond a dead center relation to itsconnections with the slide and crank whereby radial components of forcein the action kof the clutch are minimized.

HARRY A. KNOX.

